Experimental and predicted excess molar enthalpies of binary mixtures containing 2,2′-oxybis[propane], benzene, butan-1-ol, 2-methylpropan-1-ol, 2-methyl-2-ene-1-propanol at 303.15 K
Introduction
From a practical point of view, oxygenated compounds, such as ethers and alkanols, are increasingly being used as additives to gasolines owing to their octane-enhancing and pollution-reducing properties [4]. From a theoretical point of view, the study of the thermodynamic behavior of binary mixtures involving branched monoethers, such as diisopropylether with different nature of alcohols, are, of high interest because they make possible to study a number of effects (e.g. steric, proximity or orientational effects…) on the interactions present in the mixtures considered and to test group contribution models for estimating the thermodynamic excess functions of mixtures.
The present work forms a part of our investigation on binary and ternary mixtures containing oxygenate additives (ethers, alcohols) with hydrocarbons (cycloparaffins, aromatics) [1], [5]. Previously, we have reported excess enthalpies of DIPE + benzene, +toluene, +m-xylene, +cyclohexane at 303.15 K [1], [5]. As a continuation of that work, similar measurements have been made for six further binary mixtures: diisopropylether + butan-1-ol, +2-methylpropan-1-ol (isobutanol), +2-methyl-2-ene-1-propanol (isobutenol), benzene + butan-1-ol, +2-methylpropan-1-ol (isobutanol), +2-methyl-2-ene-1-propanol (isobutenol).
Section snippets
Experimental
Excess molar enthalpies were measured at HE and constant pressure, using a C80 calorimeter (Setaram, Lyon, France), a Calvet type microcalorimeter, with no vapor space, the mercury is used to separate the two cells which contained the liquid under study. Details of the equipment and its operation have been described previously [1], [6]. Over most of the mole fraction range, the errors in the mole fractions of the binary mixtures are estimated to be less than 0.001.
Diisopropylether (DIPE) and
Results and discussion
Experimental values of excess molar enthalpies HE at 303.15 K and atmospheric pressure for the six binary mixtures are listed in Table 1, Table 2. These values have been fitted with the following smoothing function, Ref. [9]:and standard deviation σ for each representation is defined aswhere N is the number of experimental points and n, the number of parameters of smoothing function (1). Values of coefficients ak and standard deviation σ, are given in
DISQUAC model
The DISQUAC model elaborated by Kehiaian [2], [3] and based on the reticular model of Guggenheim–Barker [15], [16], was applied using the same equations as reported previously [6]. The interactional terms in the thermodynamic properties, GE and HE contain a dispersive (DIS) and a quasi-chemical (QUAC) term, which are calculated, independently by the classical formulas and then simply added.
Conclusion
Using structure-dependant parameters, the model DISQUAC describes consistently the excess functions GE and HE of the investigated systems.
A comparison between experimental data and DISQUAC results is presented in a graphical way in Fig. 1, Fig. 2, Fig. 3, Fig. 4.
- ak
parameter of smoothing (Eq. (1))
- xi
molar fraction of compound, i
- xj
molar fraction of compound, j
- N
number of points
- ZE
excess molar enthalpy HE or Gibbs energy GE in J mol−1
- Exp
experimental value
- Calc
calculated value
- σ
standard deviation in J mol
List of symbols
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